1. Field of Invention
This invention relates generally to an improved filtering system and method. More particularly, this invention relates to an improved filtering system and method for incubators.
2. Background
Incubators provide an isolated and controlled environment for the maintaining of cells, tissues and various organisms in vitro during storage, manipulation and examination. Although it is known to filter the gaseous environment of the incubator to remove particulate materials, it has not been recognized that volatile organic compounds may be present within the incubator chamber which could have a deleterious effect on the samples within the chamber or on the process or manipulation being undertaken.
These undesirable volatile compounds may arise from a variety of sources and in a number of different ways. Such volatile compounds may be present in the atmosphere of the room in which the incubator is located and emanate from the gasing-off of many materials such as the glue used to set the tiles in the floor, fabrics present in the room and many other unsuspecting sources. When the incubator is opened, such undesirable volatile compounds will enter the incubator chamber. The supply of gases such as CO.sub.2 and O.sub.2 to the incubator environment from an external supply may be an unsuspected source of the undesirable volatile organic compounds.
Additionally it has been found that the materials used in the incubator for holding the specimens may be a source of such compounds. Sterile plastic ware such as used for petri dishes may off-gas styrene, ethyl-benzine and benzaldehyde. The media used in the culturing techniques such as mineral oil may also contribute to the unwanted volatile organic components.
While conventional incubators provide for airflow and filter out solid particulate material, none have recognized that there are sources of objectionable volatile organic compounds that may enter the incubator, or develop within the incubator, that should be filtered out to improve the quality of gaseous atmosphere of the incubator.
A controlled atmosphere enclosure is disclosed in U.S. Pat. No. 4,701,415. According to the disclosure of that patent there is a thermally insulated inner chamber containing a controlled gas atmosphere of carbon dioxide. The atmosphere of the inner chamber is drawn out, and the level of carbon dioxide is measure and increased if necessary. The carbon dioxide adjusted atmosphere is then filtered through a high efficiency particulate arresting (HEPA) filter to remove particulate and the filtered or non-particulate gas is then passed through a humidifier and returned to the inner chamber. This controlled atmosphere device only utilizes a HEPA filter. There is no recognition in this disclosure of the problem of gaseous impurities and no provision for their filtration.
Another controlled environmental chamber apparatus is disclosed in U.S. Pat. No. 5,169,217. The apparatus disclosed in this patent includes a chamber for maintaining biological material under controlled conditions of temperature and/or humidity having a door for controlling access to the chamber. A source of HEPA--filtered air flows downward in front of the door creating a curtain of air when the door is opened to prevent unclean air from entering the chamber. This disclosure also fails to recognize the problem of volatile organic contaminants and the desirability of their filtration.
U.S. Pat. No. 5,352,414 discloses an incubator unit and filter system for performing radioactive experiments. According to the disclosure of this patent, the chamber is provided with static filters and the gas exhaust line is provided with an exhaust filter. According to the patent, the gas used in the incubator environment is flushed through the chamber and exits through the exhaust filter. After flushing, the chamber is sealed off during the experimentation period. After the experiment, the chamber is flushed again to remove the contaminating gases and volatiles. According to the disclosure of this patent, during the experiment, radioactive active gases or other contaminants will be released into the chamber and will tend to be picked up by the charcoal paper sheets. This patent is especially concerned with radioactive gases. There is no recognition of the problem of undesirable volatile organic compounds. Additionally, there is no recognition of the desirability for recirculating the gaseous environment of incubator to filter the volatile organic compounds from the gaseous environment.